A Study of X-Ray Residual Stress Gradient Analysis in Thin Layers with Strong Fibre Texture

The mechanical properties of thin hard coatings like resistance to abrasive wear are known to depend strongly on the texture as well as on the distribution of the residual stresses over the layer thickness. The analysis of these stresses in thin coatings by means of X-ray diffraction, however, is rather difficult because the diffraction volume remains small in many cases and the stress fields are often superimposed by gradients of the texture and/or the chemical composition. By the example of PVD Ti1—xCrxN coatings with pronounced 〈111〉 fibre texture, we compare several methods in X-ray stress analysis with respect to their suitability for the detection of non-uniform residual stress distributions. The best results are obtained by means of the scattering vector method, where the depth profiles of the lattice spacings, dφψ(hkl, τ), are measured at fixed positions (φ, ψ) with respect to the sample reference system after stepwise rotation of the sample around the scattering vector gφψ.